Teletypewriter station



June 27, 1939. "r, LkcoRwlN Er A| 2,163,668 TELE'IFEWRITER STATION yFiled March l, 1935 I; L. co/eW//v NVENTORSJ L. HYS/(0 ATTORNEY PatentedJune 27, 1939 UNITED STATES PATENT OFFICE TELETYPEWRITER STATIONApplication March 1,

f 8 Claims.

This invention relates to `station circuits for teletypewritervcommunication systems of the type whereby exchange service may be givento subscribers at outlying points from the nearest teletypewriterswitching point over available telephone lines to the subscribersstation.

One object of the invention is to provide-improved arrangements wherebyrecall and disconnect signals may be .sent from s uch a station circuit.l

Another object of the invention" is 4to provide circuit arrangementswherebyseryice may be given on an unattended basis, i. e., that,messages may be recorded upon the subscribers :teletypewriterinstrument when nol person is present at the subscribers station.

Other objects are generally to improve ter minal station arrangements ofteletypewriter systems.

'20 In the patent of Hysko-Large-Munro, No. 2,093,080, granted Sept. 14,1937, are disclosed the essential elements of a teletypewriter systemfor providing teletypewriter switching service to a subscriber withoutextending to his station a long telegraph line including expensiverepeater and terminal equipment. In accordance with that system asubscriber may beA connected by a carrier channel extending through hislocal telephone exchange and other lines of a telephone exchange networkto the nearest or other suitable teletypewriter exchange switchingpoint. At the teletypewriter switching point is a teletypewriter jackcircuit extending to a circuit consisting ofoscillator-modulator-demodu- L lator equipment which may be called ateletypewriter carrier terminal circuit. The carrier .channel from saidteletypewriter carrier termi- Lnal circuit extends to multiple jacks atatele- I phone toll board through a teletypewriter control circuit andthence through any number of .telephone exchange offices to the officeat which the subscribers line terminates and thence to ,anoscillator-modulator-demodulator circuit at the subscribers oice.

At the teletypewriter switching circuit, a jack is connected to aconductor, lead or line extending, in general, to a teletypewriterexchange system. Means are provided whereby supervisory conversationsbetween the teletypewriter and the telephone toll operators relative toputting through a teletypewriter call proceed to the telephone tollboard circuit over a voice circuit, but when the operator at theteletypewriter eX- change switching point plugs a teletypewriter cordcircuit` into the teletypewriter trunkv there- 1935, serial No, 8,862

(cl. 17a- 4) at, the telephone toll line circuit is seized for thetransmission of voice frequency waves modulated in accordance withteletypewriter signaling impulses to the outlying subscriber.

A part of the system disclosed in said patent consists of the equipmentat the outlying subscribers station, said equipment being illustrated inFig 7. By reference to said Fig. '7, one observes that from the outlyingsubscribers station equipment there proceed the tip and ring conductorsGOUT and BUUR of the telephone line extending to a telephone exchangeand terminating thereat in the usual supervisoryrequip'- ment. It willbe understood, however, that the operator at said exchange has noteletypewriter instrument for communicating with the outlyingsubscriber, her sole function with respectto a particular line being topass the call on by telephone supervision to other operators so that acircuit may ultimately be set up to connect the outlying subscriber to ateletypewriter operator at a teletypewriter switching point.Communication over the telephone lines of the system is solelyby voicefrequency carrier current modulated Ytelegraphically. Inasmuch as thepresent invention deals solely with features of the outlyingsubscribers, station, the rest of the system will not be described,reference being made to the Hysko-Large-Munro patent above referredto-for a disclosure thereof. For the purposes of the present inventionit may be assumed that the line arriving at the subscribers station hasthe transmission characteristics of a local telephone line, that theclosure `of the tip and ring at the subscribers station operates a linesignal at the subscribers telephone exchange in accordance withtelephone practice, that the operator at the subscribers telephoneexchange may apply ringing current to the ringing side of the line tosignal the subscriber, that the operator at the subscribers telephoneexchange may apply ringing current to the tip side of the line to startthe motor of the local teletypewriter subscribers station and performother functions as will be described hereinafter, that carrier currentwaves arriving .over the line represent spacing impulses sent under thecontrol of distant telegraphic apparatus, that absence of carriercurrent on the line represents marking impulses sent under control ofdistant vtelegraphic apparatus, that carrier wave impulses applied tothe line by the outlying subscriber represent 4spacing' Y impulses andabsence of carrier waves represents marking impulses whichA may VYbereceived and interpreted by distant telegraphic apparatus and that at adistant teletypewriter operators position there will be found apparatusto give a recall or disconnect signal which apparatus is responsive tospacing signals of approximately five or more seconds duration sent bythe outlying subscriber from his station. With the understanding ofthese matters, the following description may be conned to the equipmentat the out- 'lying subscribers station.

The essential elements of such equipment are diagrammaticallyillustrated in the accompanying drawing, the sole figure of which is adiagrammatic representation of the elements constituting the improvedsubscribers station in their circuital relationship to one another.

rl'he principal elements of the system as specifically embodied,comprise a ringer 102 normally connected to the ring side 600B, of theincoming line; a transmitting relay 100S; a receiving selective circuit1,08 tuned to 690 cycles; an amplifying tube 106; detecting rectiers 101of any suitable type; a transmitting oscillator 100T adjusted totransmit a frequency different from the incoming frequency, for example,in the present case 1640 cycles; a suitable 60 cycle or otheralternating current power source 60 AC; a power rectifier RECT; sendingor transmitting contacts SC of the subscribers teletypewriterinstrument; a receiving selector magnet PM of the subscribersteletypewriter instrument; a call key CALL; an emergency stop key EMST;a recall key RK; a thermal timing relay A; and control relays, keys andother. equipment which will hereinafter be described in connection withthe operation. The thermal timing relay A is a device which controls itscontact several seconds after energizing current is applied to itswinding. Such aV device is well known in the art. This element typies,in the general case, any slow-acting device or relay having the timedelay characteristic of a thermal relay, In general, such devices are.adjustable with respect to their time of delay and in the present caseit is assumed that the delay time is approximately ten seconds.

Subscriber calls the central oice Y Let it be assumed that the equipmentis in normal inoperative position and the subscriber wishes to call theteletypewriter operator toy be connected. through the teletypewriterswitching point to some other subscriber. The local subscriber closesthe switch l and the call key CALL. The relay l operates and suppliespower to the rectifier RECT. The rectifier immediately energizes therelay E over an obvious circuit and the contact of relay E locks up therelay 2. The contact of relay 2 supplies heating current to thefilaments of the tubes in the amplifier 106, the rectifier RECT, theoscillator 'If, and the driving ino-tor of the teletypewriter machine.Current is supplied from the positive side o-f the rectifier RECT toenergize the relay D which, upon operating, connects the tip BOUT, 600Rto the input circuit of the tuned network 108 and to the Varmature ofthe relay 100s through the repeating coil and opens the circuit to the Erelay and to the ringer 102. The rectifier RECT supplies current in apath extending from its negative terminal through the right back contactof relay C, left back Contact of relay B, through the contacts SC of theteletypewriter to the right-hand Winding of relay S and thence to thepositive terminal of the rectifier.

IntheA meantime, upon operationof relay D and closure of the linethrough the primary of repeating coil 105, a signal lamp has appearedbefore the telephone operator at the subscribers local telephone oiiice,and the operator has caused the line 600T, 600R to be extended throughto a teletypewriter switching operator at a teletypewriter exchangeswitching point in the manner described in the aforementioned Hysko-Large-Munro patent, or in any other suitable manner, it being immaterialto the purposes of the present invention how or Where the line 600T,600B terminates at a teletypewriter switching point or at a pointcapable o-f sending and receiving and interpreting the kinds of currentswhich are to be sent and received over sai-d line for the desiredcommunication purposes, provided it does terminate at a point soequipped with the necessary apparatus.

The distant teletypewriter operator will now operate her sending machinewhich will cause transmission of interrupted or modulated carriercurrent of 600V cycles which will come in over the line. Theinterruption will cause corresponding impulses of current toy besupplied by the rectifier 101'to operate the printer selector PM. Theselector magnet will select for recording on the machine a message ofinquiry or notice that the operator is ready to learn the wishes of thelocal subscriber. The machine will then be operated to control thecontacts SC and inform the teletypewriter operator with which stationcommunication is desired. The contacts SC will control the relay 100S tointerrupt the carrier current of 1640 cycles frequency in accordancewith teletypewriter code and send to the line groups of carrier impulsescorresponding to the desired message. After the teletypewriter operatorhas connected the subscriber through the teletypewriter switching pointwith the desired distant subscriber, the local subscriber and thedistant subscriber may communicate back and forth until they haveexchanged and recorded whatever message or messages they desire to sendor receive.

Local subscriber receives a, call ing the switch ll and the call keyCALL. Thereupon, when the local subscriber types readyor his stationnumber, the distant teletypewriter operator receives his message and isimmediately enabled to send and cause to be recorded on the ,subscribersteletypewriter machine the information concerning who is calling.Communication takes place as before.

Unattended service Let us assume now that the local subscribers stationis completely unattended but that nevertheless he desires to receive anymessages from lany teletypewriter station on the communication networkAwhich might wish to send a message Upon learning over a telephone Y.

to himduring his absence. In this case, the sub- 75 scriber must alwayslleave the switch I closed during the time the station is unattended.When the switch l is closed and the distant teletypewriter operatorreceives no reply, she communicates this fact to the subscribers localtelephone operator who sends impulses of alternating ringing currentover the tip GOUT of the line to the local subscribers unattendedstation. This current willV pass through the alternating current windingof the relay E and cause the relay E' to operate. The operation of relayE will produce the same resultsV as would the operation of the callingkey CALL in that the relay 2 will be energized and the filaments of theamplifying and oscillating tubes and the drive moto-r will be energized.Upon operation of the relay E and as soon thereafter as the relay 2 hasoperated, the relay E will be locked up over a circuit from thelpositive terminal of the rectier RECT, through the right-hand winding ofrelay E and the left-hand make-upon-release contact of relay C, back tothe negative side of the rectifier. Under this condition, incomingmessages of any length may be recorded on the local subscribersteletypewriter instrument solong as the instrument is furnished with asuitable and suicient paper supply and other accessories commonlyutilized in such cases.

Termination of a communication When the local subscribers station isconnected with the teletypewriter exchange operator or through theteletypewriter exchange to a distant station, the communication may beterminated by any operator or party connected to the circuit by thesending of an upper case H code combination. This code combinationoperates a special pull bar in the teletypewriter machine marked uppercase H to close the; contact 3. This energizes the relay C over acircuit from ground, through the contact 3, through the winding of relayC, a resistance 4 and back to the positive side of the rectifier RECT.Upon operating, the

.left-hand armature of relay C transfers the holding winding of relay Eto a. circuit through the contact of the thermal relay A, back to thenegative side of rectifier RECT. The inner right make contact of relay Ccloses the heater circuit o-f thermal relay A and the outer right makecontact of relay C interrupts the circuit through the sending contactsSC, thus causing the sending upon the line of a break signal of aduration lasting until the thermal relay A opens its Contact. This breaksignal on the line energizes a lampI at the teletypewriter operatorsposition indicating to her that the circuit is to be taken down. Usuallyshe will challenge on the line first before taking the circuit down.'I'he relay C remains operated and the path through the contacts SCremains open until the heater element of the thermal relay A is heatedsufliciently to open its contact. The time necessary to do this may bechanged by selection of a suitable relay A or adjustment of the relayselected. We assume in the present case that it is approximately tenseconds. When the Contact of thermal relay A opens the locking path ofrelay E through the contacts of relay C it is opened, thereby causingthe relay E to release, it being understood that the contact 3 hasremained closed only momentarily. The relay E releases, thereby causingthe relay 2 to also release. The relay D releases because it receivesnofurther energizing current from the rectifier RECT, thereby restoringthe ring and tip of the line to the ringer 102 and the alternatting anylong break signal to the line.

ing current winding of relay E, respectively. This gives a disconnectsignal on the line 600T, 600B to the local exchange telephone operator.The laments of the tubes are deenergized and the circuit is fullyrestored to normal condition.

- Recall signal Assume now again that the subscribers station circuit isconnected through for communication with a distant subscriber and thelocal subscriber wishes to call the teletypewriter exchange operator forany purpose-- The subscriber does this by operating the recall key RK.The circuit is closed from the positive side of the rectier RECT throughresistance 4, winding of relay B, right-hand normally made contact ofrelay B and key RK to ground. The relay B operates and locks up on itsright-hand front contact through the normally made contact of relay A toground. 'I'he inner left front contact of relay B closes a circuit forthe heating element of the relay A and the outer left armature of relayB opens the circuit through the contacts SC'. This puts a break impulseupon the line which lasts until the relay A opens its conta-ct. rAsdescribed in the application of Hysko, Large and Munro, this breakimpulse causes the energization of a supervisory recall signal at theteletypewriter exchange operators position and upon noting the signalshe challenges upon the line to determine the subscribers wishes.However, the recall signal does not appear until the relay A has openedits contact and caused the restoration of the relay B and reclosing ofthe circuit through the contacts SC so that when the operator challengesthe local subscriber is immediately in a position to answer.

Among the incidental features of the system are a jack 5, by means ofwhich any suitable apparatus may be connected to the line for testingpurposes; a switch LT constituting a local test key which may beactuated in case the subscriber wishes to test his teletypewritermachine. without impressing signal impulses upon the line. The

operation of this key opens the operating circuit to the relay D thusallowin-g the ringer 102 to remain in the ring sideV of the line torespond to an incoming call. The key also connects resistance 5 acrossthe repeating coil 105 to terminate the circuit. The circuit may then beoperated as described under Subscriber Calls the Central Oice and anytest of the entire equipment can be made without calling the centraloffice. When restoring the circuit to normal, the switch I must beopened before the key LT is restored to normal.

The normal method of stopping communication and causing the drivingmotor of the teletypewriter machine to cease operating is bytransmitting a suitable special code combination such as thatcorresponding toI upper case H. However, another key EMST is providedwhich may be used in emergencies or otherwise for shutting down thelocal subscribers station and rendering all the elements thereof normalwithout transmit- This is done simply by actuating the key EMST tooperate the circuit in which it is located to thereby cause the relay 2to release.

The repeating coil 105 and the impedance balancing network connected tothe secondary thereof; the elements constituting the tuned circuit 108;the elements of the oscillator TOUT; and other elements, such` asresistances and transformers of the circuit, are of such nature thattheir purposes and functions will be readily understood by those skilledin the art Without further description.

What is claimed is:

1. A teletypewriter station, including various instrumentalities havinga non-energized nonreceiving condition and an energized receivingcondition, and including a relay having contact means for holding saidstation in one of said conditions, said relay being provided withseparate direct current and alternating current Windings whereby it maybe energized with uctuating current or direct current With the sameeiect upon its contact means, an incoming line, said alternating currentwinding being normally in.- cluded in said incoming line, and said-direct Current winding being included in a path in series with a directcurrent source when said relay is energized.

2. A teletypewriter station comprising means for receiving ortransmitting messages over a line, said means being normallyinoperative, a device having a part movable to a certain position tocondition said means for operation, said device being controllable byfluctuating current received over said line to move said part to saidposition, and an instrumentality operable under control of said part tocause said device to retain said part in said position.

3. A teletypewriter subscribers station comprising sending contacts forsending telegraph signals, a source of oscillations connected to saidcontacts to be controlled thereby, and means for impressing upon orremoving the oscillations from an outgoing line to produce marking,spacing and break signal impulses, said station also comprising adelayed action relay, a quick acting relay and a key, means whereby saidkey upon being actuated actuates said quick acting relay to impress abreak signal impulse upon said outgoing line, means whereby said quickacting relay after the initiation of said break signal is placed underthe influence of said delayed action relay and circuit arrangementswhereby upon operating said delayed action relay terminates said break-sig'nal and restores said quick acting relay. A

4. A teletypewriter system including a relay delayed in action forseveral seconds, a teletype-i writer machine Vin said system having acode selected element, a-line connectable with'said machine, meanswhereby actuation of said element applies a special condition to saidline and also energizes said relay, and devices whereby said ree layremoves said condition from said line after its operation at the end ofseveral seconds.- Y

5. A teletypewriter station having an incoming line and a slow actingrelay having the time delay characteristic of a thermal relay, twodistinct instrumentalities operable to control the opening of said line,and energizing paths closed by either of them upon their actuation tocause said relay to delayedly close said line.

6. A station, according to claim 5, in which one of theinstrumentalities is operable by suitable potentials on the incomingterminals of said line.

'7. A teletypewriter system comprising a transmission line for selectingimpulses, a printing telegraph instrument having a number of elementsselectable by various combinations of said impulses including onespecial element, a circuit varying device immediately operable by theselection of said element to condition said line, and another circuitvarying device operable after a period of seconds under the control ofsaid element for removing the condition from said line. 8. Ateletypewriter station including terminals for connection to an incomingline, teletypewriter mechanism, a control relay, an energizing source ofcurrent for said mechanism, said control relay being operable either byalternating currents received over said terminals or by locally produceddirect currents to connect said mechanism to said source in energizingrelationship, means for conducting alternating currents to said relayfrom said terminals, and means for applying direct currents thereto froma local source.

THOMAS L. CORWIN. JOHN L. HYSKO.

